The present invention relates to an arrangement for controlling a drive engine in a range of an engine ignition map when changing up a variable-speed transmission downstream in the power flow in order to reduce engine torque, comprises a gear changing device and a switching stage operatively associated with the gear changing device such that a gear-change detection signal is generated at initiation of changing up by the gear changing device and causes the switching stage operating as a function of an engine operating point to transmit a trigger signal for bringing an actuator into a position for reducing the engine torque when an engine operating point is in a described range of the engine ignition map.
In a known control arrangement as shown in German Patent 3,512,603, the gear change detection signal for the start of changing up is obtained exclusively by evaluating the variation in the engine speed. This is done to make available, as it were, a replacement signal for reversing this switching stage in order, in the event of a malfunction, to the effect that a signal, generated by the gear changing device of the variable-speed transmission, for the start of gear changing remains ineffective with respect to the switching stage for triggering the torque reduction.
This known arrangement operates, therefore, as a so-called emergency program parallel to a second arrangement, in which the gear change detection signal for the start of changing up is generated by the gear changing device of the variable-speed transmission, as is shown in German Patent 3,512,604. In this latter arrangement, use is made as a gear change detection signal of a secondary gear change signal which depends on a transmission reaction to a primary gear change signal, is obtained synchronously with a reversal of the sense of rotation at a stallable reaction transmission member participating in the changeover, and becomes effective on the switching stage of a plant gear transmission for the purpose of triggering the torque reduction without time delay upon its occurrence.
DE 3,841,400 Al discloses a device for detecting a malfunction of the interface at one end of a transmission line, in which the interface is provided at the other end of the transmission line. This device is applied in a system for controlling a motor vehicle by signal exchange between an electronic control system of a vehicle transmission and a further electronic control system of a vehicle engine. In order to maintain the comfort of the passengers as the vehicle is driven even in the situation when, for example as a consequence of a short circuit or an interruption of an acceleration resistor in the interface circuit, the interface circuit of the engine control system malfunctions as a result of vibrations or the like during driving, in this device aims to detect or identify at one end of a transmission circuit malfunctions of an interface circuit which is provided at the other end of the transmission line. In turn, this enables a transmission of a vehicle to be smoothly controlled during the gear change by optimizing the control of the interaction of the transmission and engine systems. In the conventional device, this optimization is provided by a transmission circuit in the transmission control system and monitoring circuit also in the transmission control system. An abnormality in an interface circuit that is provided in the engine control system is thereby detected, with a signal output being fed from the transmission control system via the transmission circuit to the monitoring circuit and via the interface circuit to the engine control system. In one application, the known device is used in a fault-free mode of operation to reduce the line pressure in the transmission and the engine torque during a gear change, in order to improve the gear changing performance with regard to smoothness or freedom from jolts. If an abnormality in the interface circuit of the engine control system occurs during a gear change, the transmission control system maintains the line pressure constant instead of reducing it. The aim is to obtain self-protection in this way.
An object of the present invention is also to initiate an emergency program in the engine control arrangement when the gear change detection signal for the start of changing up is present, independently of how it has been formed, and a reduction in the engine torque is lacking despite relevant parameters of the engine operating point. It is, however, desired that such an emergency program can run as far as possible independently of the engine control.
The foregoing object has been achieved according to the present invention in an advantageous way by an emergency switching stage configured to operate as a function of the operating point of the drive engine and arranged to be moved into a position to transmit a pressure control signal for the gear changing device of the variable-speed transmission with the presence of the gear change detection signal for the start of changing up and an absence of a check-back signal indicating the position of the actuator for reducing the engine torque, and the engine operating point is in a range of the engine ignition map selected for emergency operation.
Although, in the arrangement according to the present invention, the switching stage for reducing the engine torque is integrated in the known manner in an electronic ignition trigger and the reduction in the engine torque is performed by readjusting the ignition for retardation, the emergency program is covered by the transmission control which, for each ignition action, receives a check-back signal via a status bit from the electronic ignition trigger Lack of this check-back signal causes the transmission control system to increase the working pressure during the present gear change to such an extent that the change comes rapidly to an end and a risk to the gear changing element can thus be prevented. Due to this possibility of immediate reaction in each individual gear change, it is possible to eliminate from the engine control system a transmission protection emergency program designed to reduce the engine torque.
The normal transmission protection, i.e. the reduction of the engine torque, is detected as being correctly executed when the start of transmission protection, that is to say the start of reduction of the engine torque, is followed in the transmission control by a level change in the status bit. Otherwise, the pressure piling is selected, to the extent that testing of the load and speed thresholds intrinsic to the transmission control system indicate, such that the present change per se requires transmission protection in order to reduce the engine torque. However, if the status bit has already been set before the transmission protection request from the transmission control system, false triggering is suspected in the electronic ignition trigger, and the status bit is further monitored for the case that the electronic ignition trigger terminates the ignition action too early on its own. To be precise, the pressure piling then likewise further becomes effective.
This error logic thus presupposes that the electronic ignition trigger excludes the case of the status bit being at "1" although no ignition decay takes place.
Due to the thresholds intrinsic to the transmission control system, the load range for the execution of the operating pressure piling can be defined independently of the transmission protection load range of the electronic ignition trigger, it being more sensible to select a subset hereof.